Basically the idea is to allow region lords to see the cost per 10 men of their recruitment centers, and allow them to change the buying price to make a profit or foot some of the bill for the army.
For example a lord with the best infantry center in the realm that is fully upgraded to 200 men could make 40 gold per 200 men just by raising the price 2 gold per 10 men.
Likewise, a really benevolent ruler could lower the prices of their centers dramatically to encourage a certain unit type or make refitting easier for their knights, at the cost of large sums of gold to their personal expense.
The actual cost would be secret of course, so this could lead to interesting options for intrigue and intrarealm conflict. People could accuse lords of charging exorbant fees and setting the price higher than necessary or lords could create a good public image of themselves by pretending they lowered the price when they actually didn't etc.
